Thanks for the encouragement and help! So it seems as I need to create this message handler function that is referenced in the gw.begin().. And from that point any incoming messages are routed through the function?

//
void incomingMessage(const MyMessage &message)
{
  if (message.isAck())
  {
    Serial.println("This is an ack from gateway");
  }
  if (message.type == V_LIGHT)
  {
    // Change relay state
    state = message.getBool();
    Serial.print ("State = ");
    Serial.print (state);
    // Store state in eeprom
    gw.saveState(ID, state);
    Serial.print("Incoming change for sensor:");
    Serial.print(message.sensor);
    Serial.print(", New status: ");
    Serial.println(message.getBool());
  }
}
//